1. Field of the Invention
This invention relates to an optical coupling component for optically coupling a light-emitting element and a light-receiving element on one hand and optical fibers on the other hand for two-way optical communication connector, which is designed in a quest to enhance the efficiency in transmission of optical power as well as to reduce cross-talk, and an optical connector using such optical coupling component.
2. Prior Art
An optical plug holding optical fibers, and an optical connector having an optical coupling component for use in two-way optical communication and a light-emitting element and a light-receiving element mounted therein are coupled together to form a two-way optical communication connector assembly.
Prior art references include Japanese Patent Application Laid Open No. 2000-304980 (issued on Nov. 2, 2000, referred to as literature 1 hereinafter) and Japanese Patent Application Laid Open No. 2001-13665 (issued on May 18, 2001, referred to as literature 2 hereinafter) which disclose integrated-type optical coupling components for use in two-way optical communications comprise a sending side optically functional section and a receiving side optically functional section integrally connected together by means of a joint section, and optical connectors utilizing such components.
However, the optical coupling components disclosed in the literatures 1 and 2 are ones integrally molded by using a two color molding technique, which comprise a pair of optically functional sections, and a pair of tubular protective sleeves and a joint section which sleeves and a joint section are made from a material different from the material of which the optically functional sections are made, this leads to an increased cost of manufacture.
Further, there is an unpublished earlier technique which has been developed in a facility of the assignee company of the present application and which concerns to a discrete-type optical coupling component, an integrated-type optical coupling component, and optical connectors utilizing such components which are disclosed in Japanese Patent Application No. 2004-260882 (filed on Sep. 8, 2004, referred to as unpublished literature 3 hereinafter) and corresponding U.S. application and other foreign applications.
The yet publicly unknown earlier technique disclosed in the aforesaid unpublished literature 3 relating to the integrated-type optical coupling component for use in two-way optical communication will now be briefly described with reference to FIGS. 12 and 13.
In FIGS. 12 and 13, the reference numeral 107 denotes an optical coupling component for use in a two-way optical communication connector which is called sleeve unit in this unpublished literature 3. Accordingly, the term “sleeve unit” will be used in the following explanation:
As illustrated in FIGS. 13A-13E, the sleeve unit 107 comprises a columnar sending side optically functional section 181, a receiving side optically functional section 182, a sending side sleeve 173 for positioning and protecting the sending side optically functional section 181, a receiving side sleeve 174 for positioning and protecting the receiving side optically functional section 182, a joint section 170 interconnecting the sending side and receiving side optically functional sections 181 and 182 together, a sending side flange 171 surrounding the end portion 181a of the sending side optically functional section 181 on the light-emitting element side, and a receiving side flange 172 surrounding the end portion 182a of the receiving side optically functional section 182 on the light-receiving element side. These joint section 170, optically functional sections 181, 182, sleeves 173, 174 and flanges 171, 172 are integrally molded and made from an optically transparent (light-transmissive) synthetic resin such as acrylic material or the like, for example.
An optical coupling component 101 utilizing the sleeve unit 107 will be described with reference to FIGS. 12 to 14.
In FIG. 12, the reference numeral 110 denotes a receptacle which comprises a side wall 102 and a bottom wall 103. In an optical plug receiving recess 102a defined by the side wall 102 of the receptacle 110, a cylindrical sending side optical fiber accommodating tube 111 and a cylindrical receiving side optical fiber accommodating tube 112 extend in parallel to the side wall 102 and integrally upwardly from and perpendicularly to the bottom wall 103. The bottom wall 103 has a pair of apertures 113a and 113b formed therethrough communicating with the sending side optical fiber accommodating tube 111 and receiving side optical fiber accommodating tube 112, respectively and is further formed with an optical coupling component accommodating recess 113 in the outside surface (under surface of the bottom wall 103 as viewed in FIG. 12A).
The reference numeral 104 denotes a shield cover which is divided (vertically as viewed in FIG. 12A) by a partition 140 into two portions, a lower element accommodating portion 141 for housing an element holder 105 and an upper receptacle accommodating portion 142 for housing the receptacle 110. The partition 140 is formed in its central portion with openings 140a and 140b. Suitably mounted in the element holder 105 are a light-emitting element 161 and a light-receiving element 162.
The sending side optical fiber 131 is inserted into the optical plug receiving recess 102a of the receptacle 110 from the top side as viewed in FIG. 12A and fitted and held in place in the sending side optical fiber accommodating tube 111 by means of a sending side fiber ferrule 121. Likewise, the receiving side optical fiber 132 is fitted into the receiving side optical fiber accommodating tube 112 from the top side and held therein in place by means of a receiving side fiber ferrule 122.
The sleeve unit 107 is inserted upwardly from outside of the bottom wall 103 (from the underside of the bottom wall 103 as viewed in FIG. 12A) such that the sending side sleeve 173 is passed through the aperture 113a and fitted and positioned in the sending side optical fiber accommodating tube 111 while the receiving side sleeve 174 is likewise passed through the aperture 113b and fitted and positioned in the receiving side optical fiber accommodating tube 112 until the joint section 170 is received in the recess 113, as shown in FIG. 12B. At this position, it is seen that the sending side flange 171 and the receiving side flange 172 extend beyond the surface (undersurface as viewed in FIG. 12B) of the bottom wall 103.
As is seen from FIG. 14 illustrating the sleeve unit 107 fitted in the receptacle 110 as viewed from the sleeve unit side, the recess 113 is so shaped as to be generally complementary with the outer contour of the sleeve unit 107 (defined by the flanges 171, 172 and the joint section 170). The recess 113 is formed on its inner wall surface with ridges 114 (three in this example) of a semi-spherical shape in cross-section extending in the direction of the depth of the recess 113.
The sleeve unit 107 is press-fitted and held in place in the recess 113 such that these three ridges 114 are compressed against the wall of the recess. It is also to be noted that the sleeve unit 107 has a contoured projection 170a whereby the sleeve unit 107 is positioned in place within the recess 113.
Then, the receptacle 110 with the sending side optical fiber 131 and the receiving side optical fiber 132 incorporated therein is accommodated in the upper receptacle accommodating portion 142 of the shield cover 104 such that the sending side flange 171 and the receiving side flange 172 are inserted through the openings 140a, 140b of the partition 140 into the element accommodating portion 141 housing the light-emitting element 161 and the light-receiving element 162 with the end portions 181a and 182a of the optically functional sections 181 and 182 opposing the light-emitting element 161 and the light-receiving element 162, respectively.
It should be noted here that a sending side optical signal emitted from the light-emitting element 161 enters the end portion 181a of the sending side optically functional section 181 on the light-emitting element side. The end portion 181a of the sending side optically functional section 181 is provided at its end face (lower end as viewed in FIG. 13C) with a collimating lens 181b. Thus, the incident sending side optical signal passes through the collimating lens 181b and propagates through the sending side optically functional section 181, goes out of the section through a collimating lens 181d formed on the end face (the upper end as viewed in FIG. 13C) of the end portion 181c of the optically functional section 180 on the optical fiber side, and converges onto and enters the core end face of the sending side optical fiber 131. Thereafter, the sending side optical signal passes through the sending side optical fiber 131 and is sent out to the outside.
Reversely, a receiving side optical signal incoming through the receiving side optical fiber 132 from the outside will enter the receiving side optically functional section 182 through a collimating lens 182d formed on the end face (the upper end as viewed in FIG. 13C) of the end portion 182c of the receiving side optically functional section 182 and then enters and is received by the light-receiving element 162 through a collimating lens 182b formed on the end face (the lower end as viewed in FIG. 13C) of the end portion 182a of the optically functional section adjacent the light-receiving element.
With the sleeve unit 107 described above, a sending side optical signal emitted from the light-emitting element 161 enters the sending side optically functional section 181 and is sent out to the outside via the sending side optical fiber 131 while at the same time some of the sending side optical signal readily enters the joint section 170 formed of the same optically transparent (light-transmissive) material as the optically functional sections, so that the signal may leak out from the joint section to the outside, undesirably leading to a transmission loss of the light. The receiving side optical signal incoming through the receiving side optical fiber 132 from the outside and entering the receiving side optically functional section 182 is also involved with a similar leak problem.
In addition, with the sleeve unit 107 described above, it is to be appreciated that since the sending side optically functional section 181 and the receiving side optically functional section 182 are connected together by means of the joint section 170, a portion of the sending side optical signal emitted from the light-emitting element 161 will leak into the joint section 170 and is reflected at the upper and lower interfaces between the joint section and the outside air whereby it may leak into the local light-receiving element 162 via a cross-talk path as indicated by an arrow in FIG. 12B, causing a detrimental cross-talk problem.